wright – Define commands with optional arguments

Ver­sion of \new­com­mand and \re­new­com­mand that
can de­fine com­mands with op­tional ar­gu­ments. (Pre­ced­ing the
pub­lic avail­abil­ity of such com­mands, in LaTeX 2e, and with a
slightly dif­fer­ent syn­tax.)